Nitric acid blasting composition



3,282,754 NITREC ACID BLASTKNG COMPOSITIUN Neil E. Gehrig, Schuylkill Haven, Pa, assignor to Atlas Chemical Industries, lino, Wilmington, Del, a corporation of Delaware No Drawing. Original application May 13, 1963, Ser. No. 280,128, new Patent No. 3,164,503, dated Jan. 5, 1965. Divided and this application Oct. 21, 1964, Ser. No. 411,173

13 Claims. (Cl. 149-74) This is a division of application Serial Number 280,128, filed May 13, 1963, now US. Patent No. 3,164,503.

The present invention relates to blasting agents containing nitric acid as an essential component thereof and particularly to blasting agents which are comprised of an aqueous solution of nitric acid, and an insensitive, immiscible fuel.

The compositions of the present invention have the advantage of performing as powerful explosives but do not contain a sensitive high explosive component. The present compositions are highly insensitive to mechanical shock but are sensitive to detonation when initiated by the booster or priming means commonly used to initiate ammonium nitrate blasting agents.

The compositions of the present invention are dispersions and comprise an aqueous solution of nitric acid and an insensitive, immiscible fuel. The fuel component is immiscible with the nitric acid solution and is substantially unreactive with the nitric acid component under normal conditions of mixing and storage. The compositions of the present invention are relatively stable dispersions, that is, there is little separation of the components into individual phases, for at least 8 hours and generally the compositions are stable for periods of several months. The compositions of the present invention contain nitric acid and, on the basis of 100 parts by weight of an aqueous solution of nitric acid containing between about 30% and about 80% by weight of nitric acid, generally contain from about 3 to about 500 parts by weight of an insensitive, carbonaceous fuel immiscible in the nitric acid solution. Some embodiments of the invention may also include ammonium or an alkali metal nitrate, for example, the granular mixture and solid dispersion forms of the present invention described anon.

The term immiscible as used herein is defined as an inability to form a stable, homogeneous mixture with an aqueous solution of nitric acid containing between about 30% and about 80% by weight of nitric acid.

The various suitable components, their proportions, and the physical forms of the present invention will be described in more detail in the following sections:

Nitric acid The nitric acid component of the present mixtures preferably is an aqueous solution of nitric acid containing between about 30% and about 80% by weight of nitric acid. Aqueous solutions of about 60% by Weight of nitric acid aptly suited to use in the present mixtures are readily avail-able in the commercial market. Such solutions are less reactive and much less expensive than more highly concentrated nitric acid solutions. Although a more highly concentrated nitric acid solution can be used in the present invention, the hazards of handling are not compensated by a substantial increase in the effectiveness of the final mixture. However, if desired, conwntrated nitric acid and an appropriate amount of water may be separately added and incorporated into the mixtures. Since the nitric acid and water may be separately 3,282,754 Patented Nov. 1, 1966 Nitric acid having a concentration of less than about 30% frequently yields a product which is insensitive to normal detonation means. Nitric acid having a concentration of greater than about 40% is usually preferred and generally produces a final composition having a satisfactory detonation velocity and sensitivity.

Insensitive carbonaceous fuel material The term insensitive as used herein is defined as insensitive to detonation by a No. 8 blasting cap. A No. 8 blasting cap has the explosive equivalent of 2.00 grams of mercury fulminate.

The compositions of the present invention include a fuel mate-rial which is immiscible with an aqueous solution of nitric acid. That is, the two components may be utilized to produce a dispersion. Generally hydrocarbons whether parafiinic, olefinic, naphthenic, aromatic, saturated or unsaturated are suitable as the insensitive, carbonaceous fuel component. Carbohydrate materials, for example, sugars in dry form, such as sucrose, or in solution, such as molasses, may be utilized as supplemental fuels. Examples of insensitive, immiscible, carbonaceous fuel materials suited to use in the present mixtures are diesel fuel oil, or similar petroleum products, paraffinic waxes, vegetable oils, and powdered carbon. Generally the fuel material selected for use in the present invention will depend upon the desired physical form of the final product, i.e., if a pourable liquid product is desired, a liquid or semi-liquid fuel would be utilized; if a solid product is desired, a predominantly solid fuel would be utilized. Liquid fuels which are particularly suited to use in the slurry mixtures of the present invention are refined mineral oils which are liquids at normal temperatures and have a flash point above 100 F. In the granular mixtures contemplated by the present invention, No. 2 fuel oil is eminently suited to use. The specifications for N0. 2 fuel oil are well-known and are set forth in the US. Department of Commerce Commercial Standard CS 1248. No. 2 fuel oil has a flash point above 100 F., a distillation point of 675 F. and a maximum Saybolt Universal viscosity at F. of seconds. Petroleum cuts sometimes referred to as low or partially refined oils are also suitable fuel components Generally the fuels of the present compositions are unreactive with nitric acid under normal conditions of mixing and storage, that is, little, if any, fumes of the oxides of nitrogen will noticeably be given off by the mixture. Parafiins or paraifinic-based waxes are eminently suited to use as an unctuous fuel component.

Ammonium and metal nitrate While commercially avail-able fertilizer grade ammonium nitrate is suited to use in the mixture of the present invention sodium and potassium nitrates may also be used. Preferably, the nitrate component is in particulate form, that is, having .a size that will pass a No. 8 U.S.S. screen. A nitrate component in particulate form, for example, in the form of prills, pellets or granules, is

aptly suited to use in the present mixtures.

Other additives The compositions of the present invention may include other ingredients to modify the physical properties of the mixture. For example, a particulate ammonium nitrate suited to use as a starting material in the granular form of the present compositions may, if desired, initially be treated with a thin coating of protective material to minimize attrition and leaking of the particles. For example, a thin coat of clay, diatomaceous earth, or organic agents, such as a mixture of sulf-onates of monoand/ or dimethyl napthalenes, are frequently used as additives to particulate ammonium nitrate. Generally the inorganic additives such as clay are present in an amount of from about 0.5 to about 5.0% by weight of the ammonium nitrate. The organic additives are frequently elfective in amounts as low as 0.05% by weight of the ammonium nitrate.

The present mixtures may include small amounts of a suitable surfactant, generally between about 3 and about 50 parts by weight based on 100 parts of an aqueous solution of nitric acid containing between about 30% and about 80% by Weight of nitric acid to aid in obtaining and maintaining a homogeneous mixture. Gene-rally from about 3 to about 30 parts by weight based on 100 parts of the nitric acid solution of a surfactant is sufficient to emulsify the present mixtures, however, additional surfactant, up to about 50 parts may be added without noticeable harmful effects. The surplus surfactant may be beneficial in that it supplies an additional supplemental fuel to the mixture.

The present mixtures may also include small amounts of a stabilizing material, generally between about 1 and about 20 parts by Weight based on 100 parts by weight of nitric acid solution, to prevent the water phase of the mixtures from separating from the fuel component. if either the surfactant or the stabilizer materials are insensitive, carbonaceous and immiscible in aqueous nitric acid solutions, they may aid in fulfilling the fuel requirement described in the above section relating to fuels.

The sensitivity and detonation velocity of the slurry and solidified dispersion forms of the present invention usually may be stabilized by the addition of an inert, nonexplosive propagation sustaining material, for example, expanded particulate perlite, or hollow glass balls. Gen erally about 1 part by weight of the propagation sustaining material, based on 100 parts by weight of a 60% nitric acid solution, is required to obtain an advantage and usually more than about 70 parts fails to yield further improvement. Expanded perlite, a commercially available material, is the mineral perlite, a volcanic glass composed largely of aluminum silicate, which has been put through a heating process so that it is expanded into an extremely light cellular form.

The various forms of the present invention and preferred ranges of the components in each form are discussed below:

Physical forms of mixtures The compositions of the present invention may be compounded in various physical forms, for example, 1) a granular form, that is, where a dispersion of an aqueous solution of nitric acid and an immiscible fuel is utilized to coat discrete granules of ammonium nitrate; (2) a slurry form wherein a dispersion of an aqueous solution of nitric acid and an immiscible fuel are slurried together. In a preferred embodiment the slurry form also includes ammonium nitrate; and (3) a solidified form wherein an aqueous solution of nitric acid, an immiscible fuel and ammonium nitrate .are emulsified and solidified. The latter solid emulsion form is adapted to be further modified to produce mixtures which may be molded or cast and in a short period of time will harden to a solid mixture Without further curing or treatment.

Granular mixtures The granular mixtures of the present invention utilize a particulate ammonium nitrate component. This oomponcnt may be coated or uncoated. Preferably the ammonium nit-rate is of a size that will substantially entirely pass a No. 6 mesh U.S.S. screen. Since the present granular mixtures utilize a high proportion of ammonium nitrate, the proportions of the granular mixtures will be defined as being based on 100 parts by weight of the ammonium nitrate component. Using this basis, the granular mixtures preferably contain from about 3 to about 13 parts by weight of an aqueous solution of nitric acid containing from about 30% to about by Weight of nitric acid and a total of from about 4 to about 13 parts by Weight of insensitive, immiscible, fuel material.

The granular mixtures of the present invention may be easily compounded by starting with the proper proportions of ammonium nitrate, nitric acid and fuel material and vigorously mixing the components.

Table I shows the results of a series of comparative tests of the prior art ammonium-nitrate diesel fuel oil mixtures and. the blasting mixtures of the present invention. In each test the ammonium nitrate was weighed and a weighed amount of additive or additives vigorously mixed therewith. In each test No. 2 diesel fuel oil was utilized as the insensitive, immiscible, carbonaceous fuel material. Mixes 2, 3, 5, 6, 8 and 9 are illustrative of the present invention. The nitric acid component utilized in these mixes was an aqueous solution of nitric acid containing 60% by weight of nitric acid. In compounding the illustrative mixes of the present invention, a slight cooling was noted when the components and the aqueous solution of nitric acid were mixed. When the nitric acid component was added the color of the mixture changed from an offwhi-te to a light green to a canary yellow. The illustnative mixes were allowed to stand for two hours to cure. The density of the ammonium nitrate starting material was calculated to be in the range of between about 0.8 and 0.9. After curing, the density of the mixtures of the present invention were calculated to be in the range of between about 1.1 and about 1.3. In each case the mixes were packed in a portion of ceramic pipe 3" in inside diameter and 10" in length. The pac'ed mixture was primed with a /2 pound charge of Composition B (40% trinitrotoluene and 60% cyclotrimethylen-etrinitramine). The charge of Composition B was detonated by means of an electric blasting cap and the detonation velocity of the explosive mixtures was determined by the Dautriche method wherein the velocity of the mixture being tested is compared to the known velocity of a length of detonating cord. The ammonium nitrate pellets used in mixes 1, 2 and 3 were of a size that would substantially entirely pass a No. 8 mesh. U.S.S. screen and. would substantially entirely be held on *a No. 35 mesh U.S.S. screen. The pellets were coated with about 3% by weight of finely divided clay. The ammonium nitrate prills used in Mixes 4, 5 and 6 were of a size that would substantially entirely pass through a No. 8 U.S.S. screen and be held on a No. 35 U.S.S. screen. The prills, Mixes 4, 5 and 6 were treated with about 0.05% by weight of an organic parting agent consisting of a mixture of sulfonates of monoand/or dimethyl naphthalenes. The ammonium nitrate granules used in Mixes 7, 8 and 9 were sized to substantially entirely pass through a No. 6 U.S.S. screen and be held on a. No. 35 U.S.S. screen. The granular ammonium nitrate was coated with. about 3% by weight of finely divided clay. All values in the following table are parts by Weight.

TABLE I.PELLETS Mix N0. Ammonium #2 Diesel Nitric Velocity N itrate Fuel Oil Acid (feet/sec.)

P RILLS TABLE I.-Corrtinued GRANULES 100 6. 1 Failed 100 6. 2 3. 2 5, 577 100 6. 2 3. 2 5, 577

U.S.S. screen. The nitric acid component in each mix was an aqueous solution of nitric acid containing 60% by weight of nitric acid. For example, in Mix 15, 5.0 parts by Weight of No. 2 diesel fuel oil, 3.3 parts by weight of granulated sugar, and 8.7 parts by weight of an aqueous solution of nitric acid (containing 60% by weight of nitric acid) were added and thoroughly mixed with 100 parts by weight of ammonium nitrate. The mixture was then packed into a 3" x 10 ceramic pipe and primed with a /2 pound charge of Composition B. The detonation velocity determined by the Dautriche method was 9992 feet per second. The other mixes shown on Table III were compounded and tested in a similar manner. The particulate carbon and glucose mixture of Mix 17 was a waste product of a sugar refinery and consisted of spent activated carbon saturated with glucose.

TABLE III Parts by weight Mix Form of Detonation No. Ammonium Granu- Mixture of 60% Velocity Nitrate Ammonium #2 Diesel lated Molasses Particulate Nitric (feet/sec.) Nitrate Fuel 011 Sugar Carbon and Acid Glucose 15. Prills 100 5.0 8.7 9,992 16 Pellets 100 5.0 12.5 9,703 17 .-...d0 100 5.0 12.5 9,055

partially refined oil, Atreco F oil, a product of Atlantic Refining Company. The nitric acid component used in Mixes 12, 13 and 14 was an aqueous solution containing 60% by weight of nitric acid. The various additives in each mix were separately added and incorporated into the ammonium nitrate material by vigorous stirring. The mixes were each packed into a portion of ceramic pipe and primed with a high velocity booster, for example, Mixes 10, 11, 13 and 14 were primed with a 750 gram charge of gelatin dynamite and Mix 12 was primed with a /2 pound charge of Composition B. The booster was fired by means of a blasting cap. The detonation velocity of the mixes was determined by the Dautriche method. In Mix 13, for example, 7.6 parts by weight of a low refined oil (Atreco F oil). 3.8 parts by weight of finely divided diatomaceous earth and 5.9 parts by weight of an aqueous solution of nitric acid (60% by weight nitric acid), were mixed with 100 parts by weight of particulate ammonium nitrate. The mixture was then placed in a 3 x 10" portion of ceramic pipe (3" in diameter and 10" in length) and primed with 750 gram charge of gelatin dynamite. The detonation velocity of the mix, as determined by the Dautriche method was 7636 feet per second. The other mixes shown on Table II were similarly compounded and tested except that Mixes 10 and 11 contained no nitric acid component.

Slurry mixtures The present invention also provides blasting agents in the form of dispersions which may be compounded in slurry form. The blasting slurries contemplated by the present invention are pourable and liquid or semi-liquid in nature. Since the mixtures of the present invention in slurry form contain an aqueous solution of nitric acid and may be compounded without ammonium nitrate, the proportions of the slurry mixture are based on the nitric acid component. Based on 100 parts by weight of an aqueous solution of nitric acid containing between about 30 and about 80% by Weight of nitric acid, the slurry mixtures include from about 3 to about parts by weight of an insensitive, immiscible, carbonaceous fuel independent of the amounts of surfactant and stabilizer. The slurry mixtures of the present invention may, in addition to nitric acid and fuel, contain an ammonium, potassium or sodium nitrate component. In such case, based on 100 parts by weight of an aqueous solution of nitric acid containing between about 30 and about 80% nitric acid, up to about 550-parts by weight of the nitrate component may be included. An advantage of the slurry mixtures of the present invention which contain nitric acid and either ammonium or potassium nitrate is that under normal conditions such mixtures exhibit neither the amount of normally titratable TABLE II Mix Ammonium Diato- 60% Cartridge Detonation No. Nitrate Oil maceous Nitric Size Pruner Velocity Earth Acid (IL/second) 10 100 7 .7 3 .7 3 x 10 750 grams gelatin dynamite- Failed l1 100 7.7 3.7 6 x 10 do Failed 12 100 7.6 3.8 5.9 3 x 10 pound Comp. B. 7,636 13. 100 7 .5 3 .8 5 .9 3 x 10 750 grams gelatin dyna 7, 681 14 100 7.6 3.8 5.9 4 x 10 do 7,717

Table III shows the results of a series of tests of the blastin agent mixtures of the present invention containing carbohydrate material as a supplementary fuel material. In each mix, the particulate ammonium nitrate component was coated with about 0.05% by weight of the organic parting agent used in Mixes 4, 5 and 6 of Table I and was of a size which would substantially entirely pass a No. 8

U.S.S. screen and substantially entirely be held on a No. 35 quirements of the present invention is a refined hydrocarbon oil from which substantially all unsaturated hydrocarbons have been removed. Mixtures which contain relatively small amounts of nitric acid, as compared to the amount of the nitrate component, for example, those containing at least about 300 parts by weight of the nitrate component as compared to 100 parts by weight of nitric acid solution, are generally found to be thick, almost paste-like mixtures while mixtures containing a greater amount of nitric acid tend to be fluid and generally are quite fiowable mixtures. The thick, almost paste-like mixtures frequently are suitable starting materials for producing the solid mixtures of the present invention which are described below. Because the slurry mixtures are fluid the particulate nitrate starting material need not be coated with clay or other parting agent. The aqueous nitric acid solution of the present invention exhibits a preferred sensitivity when they contain at least about'40% by weight of nitric acid.

The slurry mixtures of the present invention are in the physical form of stable dispersions. The present dispersions evidence no separation of components when stored at temperatures in the range of 75 to 85 F. for periods of at least 8 hours. Frequently the present dispersions are stable for periods of 6 months or more.

An acid-resistant stabilizer in an amount between about 1 and about 10 parts based on the weight of the nitric acid solution component as 100, may be added to the slurry mixture to prevent separation of the components. Generally no stabilizer is required if the slurry is mixed and used in the same 24 hour period; however, Where the slurry is to be stored a stabilizer is desirable. A high molecular weight copolymer of methyl vinyl ether-maleic anhydride is a useful stabilizer. The product sold under the tradename Gantrez AN-169 by General Aniline & Film Co. is a copolymer of methyl vinyl ether-maleic anhydride having a mol weight of about 1,250,000 and is suited to use. A low density colloidal silica is a useful stabilizer. The product Cabosil M5 manufactured by the Cabot Corporation is suited. Synthetic polymers and copolymers, particularly those of ac-ryla-mide, have been found suited to use as stabilizers. A mixture of such polymers and copolymers, sold under the tradename Cyanogum 41, a product of American Cyanamid Co., is a suitable stabilizer. Other useful stabilizers, for example, are polyacrylic acid, and other water soluble acrylic polymers.

The present slurry mixtures may contain between about 3 and about 50 parts, based on the weight of the nitric acid solution as 100, of an acid resistant surfactant capable of forming an emulsion of oil in water. Generally a minimum of about 3 parts is required to form a satisfactory oil emulsion between the unctuous fuel component and the aqueous solution of nitric acid. Any excess, to about 50% based on the weight of nitric acid, yields no noticeable ill effects and may be a supplement source of insensitive carbonaceous fuel. Sorbitan monopalmitate, sorbitan monooleate and sorbitan monostearate have been found to be acid resistant and suited to use in the emulsion slurries of the present invention.

The present slurry mixtures may contain an inert, nonexplosive propagation sustaining material in an amount suflicient to stabilize the sensitivity and detonation velocity during storage of the slurries. Suitable propagation sustaining materials are, for example, perlite and hollow glass balls. Preferably the propagation sustaining materials are of a size that will pass a N0. 8 mesh U.S.S. screen. Generally a minimum of about 1 part of the propagation sustaining material, based on 100 parts by weight of an aqueous solution of nitric acid containing between about 30 and about 80% by weight nitric acid, is required to give noticeable results. Usually an excess of over about 70 parts by weight of the propagation sustaining material on the foregoing basis of nitric acid yields no obvious additional advantages.

The mixtures of the present invention in slurry form 0 may be compounded by mixing the proper proportions of an aqueous solution iof nitric acid and insensitive, immiscible fuel material together. If an additional component such as a stabilizer or a surfactant is utilized, the additional component is preferably blended with and added along with the fuel material.

Blasting agent emulsions in slurry form are contemplated by the present invention. Preferably such emulsions are compounded by initially blending an acid-resistant surfactant with an insensitive immiscible fuel component. Preferably the fuel is a refined or partially refined oil, paraffin or paraffin-based wax. If sorbitan monooleate is used as the emulsifying component, it is desirable to mix the sorbitan monooleate with a small amount of water to facilitate solution of the sorbitan monooleate in the mixture. If a stabilizing component is to be utilized in addition to the surfactant, it may be added along with the fuel-surfactant blend. The fuel-additive blend is then thoroughly mixed with the ammonium nitrate component. The nitric acid component is added and slowly stirred into the mixture and the final product heated (to a temperature Within the range of from about F, to about 150 F.) to remove a portion of entrapped air. The latter heating step increases the density of the final mixture and produces a more stable emulsion.

Table IV shows the results of a series of tests of slurry mixtures of the present invention. In Mix No. 18, 7.8 parts by weight of sorbitan monooleate and 7.8 parts by weight of water were initially blended to facilitate the latter solution of the sorbitan monooleate in the final slurry mixture, 20 parts by Weight of a refined mineral oil marketed under the name Nujol by Plough, Inc, was mixed with the surfactant-water blend. This mixture was then added to and incorporated in 264 parts by Weight of particulate ammonium nitrate. In order to speed solution the ammonium nitrate component was sized so that substantially passed through a No. 35 U.S.S. screen. 100 parts by weight of an aqueous solution of nitric acid (containing 60% by weight of nitric acid) was slowly stirred into the mixture. The mixture was stirred until an emulsion formed, at which time the mixture noticeably thickened. The emulsified product was then heated by means of a steam bath to F. While still fluid, the mixture was removed from the heat. A sample of the mixture was tested for emulsion stability by storing the sample at a temperature of from 75 to 85 F. and noting any evidence of component separation over a period of time. T he mixture in Mix No. 18 was found to have a minimum stability time of 8 hours. While a Minimum Stability Time is given for each of the mixes, it will be understood that the present emulsions may be stable for much longer periods of time. The dispersions of the present invention have a minimum stability time of at least 8 hours. The mixture was tested by packing a portion of the mixture into a ceramic pipe 3" in diameter and 10" long, primed with a A1. pound charge of Composition B. The detonation velocity determined by the Dautriche method was 8834 feet per second. The remaining mixes shown on Table IV were compounded and tested in the same manner. The surfactant in Mixes 20 through 23 was sorbitan monostearate and in Mixes 24 through 33 was sorbitan monopalmitate. In Mixes 22 and 23, a stabilizer of Cyanogum 41, a high molecular Weight mixture of acrylamide and N,N'-methylene bisacrylamide monomers, was utilized. In Mixes 24 through 33, a stabilizer of Gantrez AN169, a high molecular Weight copolymer of methyl vinyl ether-maleic anhydride. Mix 29 utilized a stabilizer of Cabosil M-5, a high grade colloidal silica. The stabilizer was added to the fuel component prior to mixing the fuel and ammonium nitrate components. In Mix 29 paraflin was utilized as the fuel and colloid-a1 silica as a stabilizer. In Mixes 34 through 36 an inert, non-explosive propagation sustaining material of particulate expanded perlite Was added to stabilize the detonation velocity and detonation sensitivity during storage.

TABLE IV Parts by weight Propagation Detonation Minimum Mix Insensitive Nitric Acid Emul- Sustaining Density Velocity Stability N0. Ammo- Immiseible sorbitan Sorbitan sorbitan (Basis: sion Material (feet/sec.) Tune nium Fuel Mono Mono- Mono 60% HNOa Water Stabi- Nitrate Material oleate stearate palmitate Aqueous lizer Solution) 264 1.5 8, 834 8 hours 264 1 .5 13,755 D0. 345 1 .5 16,000 Do. 128 1.6 20, 350 Do. 261 2 .1 l .6 16, 500 5 Weeks 345 5.2 1.5 16, 000 Do. 530 6 .4 6 .4 6 .4 1.4 300 6 months. 505 26 .7 26 .7 6 .6 1.3 14, 300 Do. 132 5.0 5.0 7.5 1.4 15,200 Do 102 20.0 20.0 7.5 1.2 17,900 Do. 62.5 40.0 40.0 7.5 1.0 14,000 Do. 358 34 .0 5 .0 10, 659 Do. 114 20.0 10.0 6.3 1.2 19,611 Do. 70 16.0 8.0 6.0 1.2 21,200 Do. 20 11.4 5.7 5.7 1.2 15,500 D0. 0 9.5 4.8 4.8 1.2 15,000 Do. 450 40 .0 13 .4 3 .3 1.2 14, 000 Do. 167 23 .4 .0 6 .7 1.2 10, 000 D0. 66 16.0 8.0 6.0 1.2 18,000 Do.

1 Mixes and 23 were thick, paste-like mixtures.

Solidi fied mixtures The present invention also contemplates solid, nitrocarbonitrate mixtures which may be molded, cast or extruded into any desired shape. The solid mixtures of the present invention are related to the slurry emulsions described above, however, instead of remaining in slurry form the mixtures solidify. The solid mixtures of the present invention require that (1) the components be proportioned within rather specific ranges, (2) the final mixture be heated to form a melt and drive off excess entrapped air. The proportions of components which are suited to form solid mixtures overlap the range of components suited to provide a slurry form of the explosive. The slurry formulas in the overlap area are thick, almost paste-like mixtures and may be transformed into solid mixtures by extending the heating step. The solidified mixtures include ammonium, potassium or sodium nitrate as a component. On the basis of 100 parts by weight of an aqueous solution of nitric acid containing from about to about 80% by weight of nitric acid, the solidified mixtures contain at least 300 parts by weight of the nitrate component. Generally satisfactory solidified mixtures based on 100 parts by weight of the nitric acid solution component contain between about 300 and about 550 parts of the nitrate component, from about 20 to about 80 parts by weight of a fuel component, and at least 6 parts by weight of an acid resistant surfactant, such as sorbitan monostearate, sorbitan monopalmitate or sorbitan monooleate, as the emulsifying agent. Usually over 50 parts of surfactant, based on 100 parts of the nitric acid component, yields no obvious benefit. The solidified mixtures of the present invention may also include a stabilizer component. Suitable stabilizer components are described in the foregoing section describing slurry mixtures. If a stabilizer component is used, it usually produces no increase in effectiveness above about 20 parts by Weight based on 100 parts of the nitric acid solution component. If any additives are utilized which meet the requirements for a fuel component, that is they are carbonaceous, immiscible and insensitive to detonation, their weight may be considered as additional fuel. Generally the mixtures of the present invention form a melt in a range between 100 F. and 135 F. and this temperature is suificient to form the present solid mixtures. For safety purposes, it is preferred that the components be chosen so that the mixture has a melting point not substantially higher than about 150 F.

The present solid dispersions may contain an inert, nonexplosive propagation sustaining material in an amount sufiicient to stabilize the sensitivity to detonation and detonation velocity during storage of the dispersions.

Suitable propagation sustaining materials are generally of a size which will pass a No. 8 mesh U.S.S. screen. Materials suitable for this purpose are, for example, perlite and hollow glass balls. Generally a minimum of about 1 part of the propagation sustaining material, based on 100 parts by weight of an aqueous solution of nitric acid containing between about 30 and about by weight of nitric acid, is required to give noticeable results. Usually an excess of over about 70 parts by weight of the propagation sustaining material on the foregoing basis of nitric acid yields no obvious additional advantages.

Table V shows the composition of a series of solidified dispersions and the results of performance tests carried out utilizing the solid mixtures. For example, Mix 37 was compounded by initially blending 35.9 parts by weight of refined mineral oil and 26.8 parts by weight of sorbitan monostearate, mixing the blend with 505 parts by weight of particulate ammonium nitrate of a size that will substantially entirely pass a No. 35 U.S.S. screen, and adding parts by weight of an aqueous solution of nitric acid containing 60% by weight of nitric acid. The resulting mixture was stirred until the mixture stiffened and then. heated from about 100 to about F. to rid the mixture of excess air bubbles introduced in the mixing operation. In Mix 39, 46.5 parts by Weight of a parafiinic-based wax (90% parafiin and 10% ethyl vinyl acetate) was utilized as the fuel component. The heated mixture was poured into a portion of ceramic pipe 3" in diameter and 10" in length. The mixture solidified in about two hours. The solid mixture Was then primed with a 4 pound charge of Composition B and the Composition B initiated by a blasting cap. The detonation velocity determined by the Dautriche method was determined to be 12,200 feet per second. A sample of the mixture was stored at temperatures ranging between 75 and 85 F. and after a period of 6 months was found to evidence no component separation. The other mixes shown in Table V below were carried out in the same manner. Mixes 41 and 42 are examples of solidified mixtures which contain perlite as an inert, non-explosive propagation sustaining material to stabilize the detonation velocity and detonation sensitivity during storage.

In general, the density of the mixtures is determined by the amount of air entrapped in the mixture. A product having a density of well over 1 may be produced by removing a substantial amount of the entrapped air. Entrapped air may be removed by placing the mixture immediately after stirring, and before it has solidified, in an open vessel and heating. In order to insure that the solid mixture will have a satisfactory sensitivity to detonation, it is desirable that a small amount of air remain in the mixture. A product having a density of from about 1.0 to about 1.4 and having a satisfactory sensitivity to detonation may be produced by heating the mixture after stirring to a temperature sufiiciently high 12 an insensitive, carbonaceous fuel immiscible in said acid solution selected from the group consisting of mineral oil, parafiin, paraffin-based waxes, vegetable oils and powdered carbon.

to form a melt. Generally such temperature is in the 7. A blasting agent consisting essentially of nitric acid, neighborhood of about 100 F. It is desirable for Safety water, an insensitive immiscible fuel, an acid resistant purposes, that the components be chosen so that the Surfactant and an acid resistant stabilizer. melting step can be carried out at a temperature t 8. An emulsified blasting agent composition consisting significantly in excess of 150 F. essentially of 100 parts by weight of an aqueous solution TABLE v Parts by weight Mix Density Detonation No. Insensitive, Gantrez Velocity Ammonium carbonaceous Sorbitan AN-lGQ Perlite Nitric Nitrate Imrniscible Monostearate Stabi- Acid Fuel lizer The term consisting essentially of as used in the claims, includes compositions containing the named components and other ingredients whichdo not deleteriously affect the compositions for the purposes stated in the specification.

What is claimed is:

1. A blasting agent consisting essentially of a stable dispersion of nitric acid,

water, and

an insensitive, immiscible fuel material,

said fuel being substantially unreactive with the nitric acid component under normal conditions of mixing and storage,

said dispersion being stable for at least 8 hours.

2. A blasting agent consisting essentially of a dispersion of a nitric acid solution having a concentration of from about 30% to about 80% by weight nitric acid, and an insensitive, carbonaceous fuel immiscible in said acid solution,

said fuel being substantially unreactive with the nitric acid component under normal conditions of mixing and storage,

said dispersion being stable for at least 8 hours.

3. The composition of claim 2 wherein the fuel material is mineral oil.

4. A blasting slurry composition consisting essentially of a stable dispersion of an aqueous solution of nitric acid, and

an insensitive, carbonaceous fuel immiscible in the said nitric acid solution,

said dispersion being stable for at least 8 hours.

5. A blasting slurry composition consisting essentially of a dispersion of 100 parts by weight of an aqueous solution of nitric acid containing from about 30% to about 80% by weight of nitric acid, and

from about 3 to about 65 parts by weight of mineral oil.

6. A blasting agent consisting essentially of a dispersion of a nitric acid solution having a concentration of from about 30% to about 80% by weight of nitric acid and 6 of nitric acid, from about 3 to about parts by weight of an insensitive, immiscible fuel material, from about 1 to about 10 parts by Weight of an acid resistant stabilizer and from about 3 to about 50 parts by weight of an acid resistant surfactant.

9. The composition of claim 8 wherein the acid resistant stabilizer is selected from the group consisting of colloidal silica, polymers and copolymers of acrylamide, a copolymer of methyl vinyl ether-maleic anhydride, polyaorylic acid and water soluble acrylic polymers.

10. The composition of claim 8 wherein the acidresistant surfactant is selected from the group consisting of sorbitan monooleate, sorbitan monopalmitate and sorbitan monostearate.

11. An emulsified blasting agent consisting essentially of nitric acid, water, an insensitive, immiscible fuel and an acid-resistant surfactant.

12. A blasting agent consisting essentially of an aqueous solution of nitric acid, an insensitive, immiscible fuel and an acid-resistant stabilizer.

13. An emulsified blasting agent consisting essentially of 100 parts by weight of an aqueous solution of nitric acid having a concentration of from about 30% to about by weight of nitric acid, from about 3 to about 65 parts by weight of an insensitive, immiscible fuel selected from the group consisting of mineral oil, paraffin, paraffinbased Waxes, vegetable oils and powdered carbon and from about 3 to about 50 parts by weight of an acidresistant surfactant.

References Cited by the Examiner UNITED STATES PATENTS 3,164,503 1/1965 Gehrig 149-18 3,242,0l9 3/1966 Gehrig l49l8 FOREIGN PATENTS 883,918 12/1961 Great Britain.

BENJAMIN R. PADGETT, Primary Examiner.

S. J. LECHERT, Assistant Examiner. 

1. A BLASTING AGENT CONSISTING ESSENTIALLY OF A STABLE DISPERSION OF NITRIC ACID, WATER, AND AN INSENSITIVE, IMMISCIBLE FUEL MATERIAL, SAID FUEL BEING SUBSTANTIALLY UNREACTIVE WITH THE NITRIC ACID COMPONENT UNDER NORMAL CONDITIONS OF MIXING AND STORAGE, SAID DISPRSION BEING STABLE FOR AT LEAST 8 HOURS. 